They have given the decay width differently, so in my understanding BR(w+ > l+ vl)=20%=10% + 10%
for muon and electron respectively, according to "MG5_v_2_6_1" but it was 10%=5% + 5%.

Now the question I have is about the cross_section :
\sigma_tot = \sigma_prod * BR(w+ > mu+ vm) + \sigma_prod * BR(w+ > e+ ve) = \sigma_prod *0.1+ \sigma_prod *0.1 (according to pdg, with the defination we have in MG5, i.e., l = mu + e; both the lepton)
But in the MG5 we have : \sigma_tot = \sigma_prod *0.1